1. Field of Invention
The present invention relates to the mobile communication field, especially, System Architecture Evolution/Long Term Evolution (SAE/LTE) in the 3G mobile communication field, and more particularly, to an Evolved Multimedia Broadcast/Multicast Service (EMBMS) access gateway, a base station, and methods thereof, which support Internet Protocol (IP) multicast.
2. Description of Prior Art
Current network architectures based on SAE/LTE are flatter than those before evolution. On one hand, a two-node architecture (base station NodeB+Radio Network Controller RNC) of radio access network portions is simplified into an one-node architecture (base station eNodeB, “eNB” for short hereinafter). On the other hand, mesh like connections are introduced. That is to say, one eNB may be connected to multiple access gateways (aGWs) via an S1 interface, and one eNB may be connected to multiple neighboring eNBs via an X2 interface. Such connections may be physical or logical. Two eNBs, if logically connected, may be physically connected via an aGW. The architecture of SAE/LTE is shown in FIG. 1.
Specifically, referring to FIG. 1, two access gateways aGW1 and aGW2 are connected to three base stations eNB1, eNB2 and eNB3 via S1 interfaces respectively, and the three base stations eNB1, eNB2 and eNB3 are connected to each other via X2 interfaces. FIG. 1 shows a situation where there are physical connections between the respective nodes. If there is no X2 interface connection between eNB1 and eNB3, than eNB1 may be connected to eNB3 via aGW1 or aGW2, so that there is a logical connection between eNB1 and eNB3.
Specifications for SAE/LTE have been defined from the time of 3GPP Re17. In the architecture of SAE/LTE, MBMS is termed as EMBMS (Evolved-MBMS). Such flat architecture brings a new challenge to efficient transmission Multimedia Broadcast/Multicast Service (MBMS) data: whether to continue to use the GTP protocol (GPRS tunneling protocol) before the Re17 version in connecting eNBs and aGWs, or to introduce other techniques. In current discussions on 3GPP, it is proposed to introduce IP multicast into the architecture of broadcast/multicast service. However, in current specifications, how to connect an eNB and an aGW on a user plane has not been defined. That is to say, 3GPP has not defined protocol architecture on the S1 interface. In the present invention, protocol architecture on the S1 interface is provided and further how to transmit MBMS control information is discussed, and thereby an EMBMS access gateway, a base station and methods thereof, which support IP multicast, are provided.
Documents proposed by Nokia and Vodafone in the 52nd Conference of RAN3 in May, 2006 (R3-060652 MBMS aspects in SAE/LTE work, Nokia; R3-060694 Support of MBMS in E-UTRAN) show that they approve of introducing IP multicast into EMBMS, with some simple analyses on how to transmit EMBMS control information on the S1 interface. For multicast services. Nokia proposes to transmit an MBMS Session Start message to eNBs included in a Service Area (“SA” for short hereinafter) and also included in a Tracking Area (“TA” hereinafter) hosting interested users. Vodafone proposes to transmit an MBMS Session Start message to eNBs included in a TA hosting interested users. Further, for broadcast services, both Nokia and Vodafone hold that an MBMS Session Start message should be transmitted to eNBs included in an SA.
However, the above two documents just proposed that IP multicast may be introduced into EMBMS, without any discussions on the protocol stack architecture and operations. Therefore, it is still unknown how to let IP multicast play a role in transmission of service data.
Therefore, there is a need for an EMBMS access gateway, a base station and methods thereof, which support IP multicast, and from which it can be known how to transmit EMBMS service data by means of IP multicast under the framework of SAE/LTE so that MBMS service data from an aGW arrive at an eNB more efficiently.
The above two documents, though giving a flow design scheme for EMBMS, have some problems in the technical aspects. For example, for multicast services, when an aGW select eNBs to which an MBMS Session Start message is transmitted, there may be a problem that some eNBs which indeed need receipt of the MBMS Session Start message actually do not receive such MBMS Session Start message.
Therefore, there is a need for an EMBMS access gateway, a base station and methods thereof supporting IP multicast, which on one hand enable an eNB to get sufficient information from an aGW, and on the other hand facilitate function implementation and flow design of the eNB in various possible situations.